Hi, OP, I'm another who says do go to the police and tell them what you've told us here.
I had something similar happen to me and thought I could handle it by ignoring him, etc. It was only when a friend came round one evening and listened to all the messages he'd left on my landline which by this time had become quite threatening, that he drove me to the police station...(me? In a police station? I'd only ever visited one before, when I'd had my car sideswiped and I needed to make a claim on my insurance...how the fuck did this happen?)
Best thing ever, going to see them. They took it all so seriously, two officers visited him and, well, laid down the law.told him that any further contact or harassment of me would result in him being immediately hauled off to the cells where he would stay until a court appearance !
They then came back to me and de-briefed.
I bloody heart my local police. They were, and are, so supportive, totally brill 
Since then, tho, I'm v.careful about my online presence. I'm still a serial name changer on forums I post to, change personal details etc..I'm very aware that tho he's running scared of contacting me directly, he may still be indulging his obsession by online stalking, so I don't give him a paper trail.
All the very, very best, and please, please, go to your local copshop, won't you?